Sensor modules with large magnetic cores typically are costly and bulky. An example of such a system 100 is shown in FIG. 1. In FIG. 1, a primary conductor 102 is put through a slit magnetic core 104 which collects all flux around conductor 102 and directs it onto a Hall sensor 106 placed in the air gap 108 of core 104. System 100 and others similar are not differential, which means such systems generally measure the magnetic field only at one location. If a background field is present, it can lead to errors in sensor output; although a significant part of the background field is shielded by the magnetic core, the suppression of background fields is usually not better than a factor of 100. On the other hand, these systems suffer from errors due to core imperfections, such as hysteresis, saturation, shift in offset after large overcurrent events and limited bandwidth due to eddy currents in the core or in the leadframe of the sensor.
Another sensor system 200 is shown in FIG. 2 and includes a sensor integrated circuit (IC) 202 with small magnetic concentrators 204 on top of the die 206. The sensor package 208 is a general purpose type, although package 208 may be modified to use a nonmagnetic copper leadframe material. Sensor IC 202 is placed above or below the primary conductor 210. System 200 is generally small and light-weight but suffers from assembly tolerances because conductor 210 is not integrated into package 208. System 200 also suffers from limited bandwidth due to eddy currents in the leadframe of the standard IC-package 208. Moreover, the suppression of horizontal background fields perpendicularly to the current trace is limited, although system 200 uses differential measurement principles (i.e., system 200 measures the magnetic field at two different places and subtracts one from the other). System 200 also needs a particular technology process to manufacture concentrators 204, which can themselves create additional errors, such as hysteresis and limited overload capability.